Status and trends of the Asian clam (Corbicula fluminea) in the lower Fox River and Green Bay

In the upper Great Lakes region, survival and population growth of the non-indigenous Asian clam Corbicula fluminea has been limited by cold climates that cause severe overwinter mortality. At these northern latitudes, Asian clam populations are often limited to thermal refugia – particularly warmwater discharges from industrial facilities. Several such facilities exist in the lower Fox River in Green Bay. Asian clams were first documented in the lower Fox River in 1999 and were extensively surveyed near the river mouth in 2011, but the few individuals found were restricted to the warmwater discharge from the Pulliam Power Plant. We performed a follow-up survey during 2017 to re-assess the population status of Asian clams in the lower Fox River at four industrial discharges, including the Pulliam Power Plant. We found more widespread evidence of Asian clams throughout the lower Fox River than previous surveys, but only one live individual was captured. We suspect that the back-to-back severe winters of 2013–2014 and 2014–2015 caused widespread overwinter mortality. Our investigation highlights the significant challenges for establishment of Asian clam populations in the upper Great Lakes region, and provides an example of a potential invasive species struggling to establish a viable population in a hostile climate.     

Impact of Zebra Mussels (Dreissena polymorpha) on Fingernail Clams (Sphaeriidae) in Extreme Southern Lake Michigan

The demography of the zebra mussel (Dreissena polymorpha) and its impacts on native fingernail clams (Sphaeriidae) in Lake Michigan near Michigan City, Indiana were studied from 1992 to 1997 at 5, 10, and 15 m depths. Zebra mussel densities ranged from 0 to 6,209/m², and were greatest at deeper stations. Size-frequency distributions suggest that initial colonization of the Michigan City area occurred in 1991, with adults typically living for 2 to 3 years. Abundance of adult populations may be limited by the sandy habitat typical of the areas studied and the occasional high-energy wave action in the shallow (5 m) near-shore zone of this area. Densities of fingernail clam ranged from 0 to 1,312/m² and were also greatest at deeper stations. Approximately half of the fingernail clams shells between 1 and 2 mm in size were used as substrate for attachment by juvenile and adult zebra mussels, while over 90% of the clams > 2 mm showed attachment by zebra mussels. Overall median densities of Sphaeriidae decreased from 832/m² to 13/m² at the 15 m depth and from 234/m² to 0/m² at the 10 m depth during the study. It appears that zebra mussel colonization caused a dramatic reduction of Sphaeriidae density by 1997 that may eventually result in their loss from the area.     

Lake-wide Distribution of Dreissena in Lake Michigan, 1999

The Great Lakes Science Center has conducted lake-wide bottom trawl surveys of the fish community in Lake Michigan each fall since 1973. These systematic surveys are performed at depths of 9 to 110 m at each of seven index sites around Lake Michigan. Zebra mussel (Dreissena polymorpha) populations have expanded to all survey locations and at a level to sufficiently contribute to the bottom trawl catches. The quagga (Dreissena bugensis), recently reported in Lake Michigan, was likely in the catches though not recognized. Dreissena spp. biomass ranged from about 0.6 to 15 kg/ha at the various sites in 1999. Dreissenid mussels were found at depths of 9 to 82 m, with their peak biomass at 27 to 46 m. The colonization of these exotic mussels has ecological implications as well as potential ramifications on the ability to sample fish consistently and effectively with bottom trawls in Lake Michigan.     

Thermal and hydrologic suitability of Lake Erie and its major tributaries for spawning of Asian carps

Bighead carp Hypophthalmichthys nobilis, silver carp H. molitrix, and grass carp Ctenopharyngodon idella (hereafter Asian carps) have expanded throughout the Mississippi River basin and threaten to invade Lakes Michigan and Erie. Adult bighead carp and grass carp have been captured in Lake Erie, but self-sustaining populations probably do not exist. We examined thermal conditions within Lake Erie to determine if Asian carps would mature, and to estimate time of year when fish would reach spawning condition. We also examined whether thermal and hydrologic conditions in the largest tributaries to western and central Lake Erie were suitable for spawning of Asian carps. We used length of undammed river, predicted summer temperatures, and predicted water velocity during flood events to determine whether sufficient lengths of river are available for spawning of Asian carps. Most rivers we examined have at least 100 km of passable river and summer temperatures suitable (> 21 C) for rapid incubation of eggs of Asian carps. Predicted water velocity and temperature were sufficient to ensure that incubating eggs, which drift in the water column, would hatch before reaching Lake Erie for most flood events in most rivers if spawned far enough upstream. The Maumee, Sandusky, and Grand Rivers were predicted to be the most likely to support spawning of Asian carps. The Black, Huron, Portage, and Vermilion Rivers were predicted to be less suitable. The weight of the evidence suggests that the largest western and central Lake Erie tributaries are thermally and hydrologically suitable to support spawning of Asian carps.     

Range Expansion of the Exotic Zooplankter Cercopagis pengoi (Ostroumov) into Western Lake Erie and Muskegon Lake

Previously reported from Lakes Ontario and Michigan, the nonindigenous zooplankter Cercopagis pengoi was found for the first time in western Lake Erie, the Detroit River, and Muskegon Lake, Michigan, during summer 2001. A native of the Ponto-Caspian region, C. pengoi is currently expanding its range in North America. Analysis of mitochondrial gene ND5 sequences confirmed that the Lake Erie haplotype is identical to that reported previously from Lakes Ontario and Michigan and the Finger Lakes, New York. These findings support the hypothesis that C. pengoi's range expansion in the Great Lakes likely resulted from inter-lake transfer of ballast water, rather than from additional introductions from European locations. Pleasure-craft traffic operating between Lake Michigan and Muskegon Lake is likely responsible for this inland transfer of Cercopagis, a trend that likely will increase due to human activities.     

Predicting the potential distribution of the non-native Red Swamp Crayfish Procambarus clarkii in the Laurentian Great Lakes

The ongoing threat of introduction of invasive species, including crayfish, to the Laurentian Great Lakes has motivated the development of predictive models to inform where these invaders are likely to establish. Our study is among the first to apply regional freshwater-specific GIS layers to species occurrence data to predict ecosystem suitability to invasions, specifically for the red swamp crayfish, Procambarus clarkii, in the Great Lakes. We combined a database of crayfish species occurrences with the Great Lakes Aquatic Habitat Framework (GLAHF) GIS layers to model habitats suitable to invasion by P. clarkii using boosted regression trees and physiological information for this species. We developed a model of all suitable crayfish habitat across the Great Lakes, then constrained this habitat to areas anticipated to be suitable for P. clarkii based on known physiological limitations of this species. Specifically, P. clarkii requires a minimum temperature of 15?°C for copulation and oviposition, with peak reproduction occurring at temperatures of 20–23?°C. We identified 2% of the Great Lakes as suitable for P. clarkii establishment and 0.88% as optimal for this crayfish, primarily located on the southern coastlines of lakes Michigan and Erie and shallow bays including Saginaw Bay (Lake Huron), Green Bay (Lake Michigan), and Henderson Bay (Lake Ontario). These predictions of where P. clarkii is likely to establish populations can be used to identify areas where education, outreach, compliance, and law enforcement efforts should seek to prevent new introductions of this crayfish and help prioritize locations for surveillance to detect newly established populations.     

First Finding of the Amphipod Echinogammarus ischnus and the Mussel Dreissena bugensis in Lake Michigan

The first finding of the amphipod Echinogammarus ischnus and the mussel Dreissena bugensis in Lake Michigan is documented. These two species are widespread and abundant in the lower lakes, but had not yet been reported from Lake Michigan. E. ischnus is generally considered a warmwater form that is typically associated with hard substrates and Dreissena clusters in the nearshore zone. Along the eastern shoreline of Lake Michigan, this species was present at rocky, breakwall habitats along the entire north-south axis of the lake. Although not abundant, this species was also found at soft-bottomed sites as deep as 94 m in the southern basin. The finding of this species in deep offshore waters apparently extends the known habitat range for this species in the Great Lakes, but it is found in deep water areas within its native range (Caspian Sea). D. bugensis was not abundant, but was present in both the southern and northern portions of the lake. Individuals of up to 36 mm in length were collected, indicating that it had probably been present in the lake for 2 or more years. Also presented are depth-defined densities of D. polymorpha at 37 sites in the Straits of Mackinac in 1997, and densities at up to 55 sites in the southern basin in 1992/93 and 1998/99. Mean densities decreased with increased water depth in both regions. Maximum mean density in the Straits in 1997 was 13,700/m² (≤ 10 m), and maximum density in the southern basin in 1999 was 2,100/m² (≤ 30 m). Mean densities at the ≤ 30-m interval in the southern basin remained relatively unchanged between 1993 and 1999, but increased from 25/m² to 1,100/m² at the 31 to 50 m interval over the same time period. D. polymorpha was rare at sites > 50 m. The presence of E. ischnus and the expected population expansion of D. bugensis will likely contribute to further foodweb changes in the lake.     

Occurrence of the Asiatic Clam Corbicula Fluminea in the Maumee River and Western Lake Erie

The Asiatic clam was found in only two locations along the southern shore of the western basin of Lake Erie: the thermal plume areas of two coal-fired power plants with once-through condenser cooling systems. Three sewage treatment plant outfalls were sampled, but Corbicula were found only in the sewage treatment plant outfall that was within the thermal plume of a power plant. No Corbicula were found in the vicinity of the nuclear power plant which has a closed-cycle natural draft cooling tower, and hence no significant thermal plume.From the age of some of the specimens, this clam has probably resided in the region since 1978. The Great Lakes are farther north than the natural range of this clam, and prolonged cold temperatures in this region may be responsible for the confinement of this clam to baseload power plants with continuous thermal plumes.     

Biological Monitoring of Organochlorine Contaminants in the St. Clair and Detroit Rivers Using Introduced Clams, Elliptio Complanatus

Introduced clams (in cages) were effective biomonitors in determining the distribution, biological availability, and source areas of a number of chlorinated organic contaminants in the St. Clair River-Detroit River corridor during 1982 and 1983. In the St. Clair River, hexachlorobenzene (HCB), octachlorostyrene (OCS), pentachlorobenzene (QCB), hexachlorobutadiene (HCBD), 2,3,6-trichlorotoluene (TCT), and alpha-BHC were most frequently identified in tissues after 3 weeks’ exposure. When compared to other locations in the St. Clair and Detroit rivers, significantly (p<0.05) higher levels of QCB, HCB, OCS, and HCBD were found in clams exposed along the Sarnia to Corunna, Ontario, shoreline. Elevated concentrations of HCB and OCS were also detected in water samples from this section of the river. TCT was found in clams from most locations, at low levels, with no obvious source area. Low levels of polychlorinated biphenyls (PCBs) were restricted to clams from the Sarnia area. In the Detroit River, PCBs, HCB, and OCS were most frequently detected in clams. PCB levels were significantly (p<0.05) higher along the Michigan shore and the highest concentrations were found in the Rouge River area. PCBs were also detected in some water samples from urbanized areas of the river. HCB and OCS were found at near-detection levels in clams from most stations. Contaminant levels in clams from around Fighting Island were low or non-detectable, indicating an absence of biologically available organochlorine contaminants in this area of the river. In the St. Clair River, p,p-DDE was only detected in the Sarnia area, whereas it was found in clams from both sides of the Detroit River, also at low levels. Aldrin, chlordane, and DDT were only sporadically detected in both rivers.     

Trends in Diporeia populations across the Laurentian Great Lakes, 1997-2009

Benthic communities in the Laurentian Great Lakes have been in a state of flux since the arrival of dreissenid mussels, with the most dramatic changes occurring in population densities of the amphipod Diporeia. In response, the US EPA initiated an annual benthic macroinvertebrate monitoring program on all five Great Lakes in 1997. Although historically the dominant benthic invertebrate in all the lakes, no Diporeia have been found in Lake Erie during the first 13 years of our study, confirming that Diporeia is now effectively absent from that lake. Populations have almost entirely disappeared from our shallow (< 90 m) sites in lakes Ontario, Huron, and Michigan. In Lake Ontario, three of our four deep (> 90 m) sites still supported Diporeia populations in 2009, with densities at those sites ranging between 96 and 198/m². In Lake Michigan, populations were still found at six of our seven deep sites in 2009, with densities ranging from 57 to 1409/m². Densities of Diporeia in 2009 at the four deep sites in Lake Huron were somewhat lower than those in Lake Michigan, ranging from 191 to 720/m². Interannual changes in population size in Lake Huron and Lake Michigan have shown a degree of synchrony across most sites, with periods of rapid decline (1997-2000, 2003-2004) alternating with periods of little change or even increase (2001-2002, 2005-2009). There has been no evidence of directional trends at any sites in Lake Superior, although substantial interannual variability was seen.     

Discovery of the Asiatic Clam,Corbicula Fluminea,in Lake Michigan

Ten live specimens of the Asiatic clam, Corbicula fluminea (Müller) were collected 22 November 1983 in southeastern Lake Michigan offshore from the J. H. Campbell Power Plant. The site is 7.6 m deep with a substrate of coarse sand and gravel. This represents the second record of Corbicula from the Laurentian Great Lakes and the first from Lake Michigan.     

Fatty acid profiles of lake trout reveal the importance of lipid content for interpreting trophic relationships within and across lakes

Fatty acid profiles increasingly are being used to quantify foraging patterns of consumers, but the associated interpretation may vary with the tissue type and its lipid content. For salmonids, lipid deposits can be found in both dorsal and ventral (“belly flap”) areas of muscle tissues. However, it is uncertain whether belly flap and dorsal muscle fatty acid profiles are similar in natural populations of fish. We examined how fatty acid profiles of belly flap compared to those of dorsal muscle and the consequent impacts on dietary inferences. Fatty acid profiles were derived from lake trout (Salvelinus namaycush) caught in five North American lakes: Champlain, Flathead, Michigan, Ontario, and Swan. Fatty acid profiles were most similar between tissues when lipid content of muscle was > ~10%, the threshold below which similarities decreased and thus increasingly affected dietary inference. Some fatty acids commonly used as trophic indicators preferentially accrued in one tissue over the other depending on lipid content of the tissues. Regardless of tissue type, fatty acid profiles were specific to each lake indicating that food web structures were distinctive over a broad geographic range. Fatty acid profiles of tissues from lakes Michigan and Ontario were highly similar, so were those from Flathead and Swan lakes, whereas those from Lake Champlain were distinct, having comparatively high proportions of 18:1n-9. We conclude that lipid storage areas like belly flaps likely provide a more accurate signal than muscle when using fatty acids to investigate dietary patterns, particularly when muscle lipid levels are low.     

Investigation of viruses in Diporeia spp. from the Laurentian Great Lakes and Owasco Lake as potential stressors of declining populations

The benthic amphipod Diporeia is an ecologically and biogeochemically important constituent of deep freshwater lakes in North America. The proliferation of dreissenid mussels in the mid-1990s coincided with a sharp decrease in Diporeia populations in several Laurentian Great Lakes; however the ultimate cause and mechanisms of their decline are still unknown. Here we examined the composition of DNA viruses associated with Diporeia collected from populations of Lake Michigan that had declined and stable populations in Lake Superior and Owasco Lake (Finger Lake in central New York State). Viral metagenomic libraries from Owasco Lake and Lake Superior were comprised primarily of bacteriophages, which may infect bacteria within the amphipod microbiome. In contrast, the metagenomic library from Lake Michigan contained well-represented ssDNA circular viral genomes. The prevalence and viral load of one putative Type V ssDNA circular virus (LM29173) that recruited almost 30% of total viral sequence reads in the Lake Michigan library was analyzed by quantitative PCR. The prevalence of LM29173 was over two orders of magnitude greater in Lake Michigan compared to the other two lakes. Although further research is necessary to establish the pathology and epidemiological extent of viral-Diporeia interactions, our data suggest that viruses may be numerically significant constituents of the Diporeia microbiome, and if pathogenic some of these viruses may be a stressor of Great Lakes Diporeia populations. Our data further indicate that special attention should be given to the circovirus that was prevalent in the declining Michigan population but uncommon in the other two lakes.     

Evidence of a remnant self-sustaining strain of lake trout in the Lake Michigan basin

Managers have long embraced the need to maintain diversity as a requisite condition for population and community sustainability. In the case of Great Lakes lake trout, diversity has been severely compromised. The identification of new gamete sources may be beneficial to lake trout reintroduction efforts, particularly in situations where native stocks have been completely extirpated such as in Lake Michigan. Lake trout from Elk Lake, Michigan, are genetically distinct from domestic hatchery strains and historical forms of lake trout from Lake Michigan. Importantly, Elk Lake fish were genetically distinct from Marquette strain lake trout which were previously stocked into Elk Lake. Elk Lake fish were most similar to Lake Michigan basin-derived Lewis Lake (LLW) and Green Lake (GLW) hatchery strains and to historical Lake Michigan populations from the Charlevoix, Michigan area. While all individuals exhibited characteristics of lean form lake trout, the body shape of lake trout from Elk Lake, stocked lean fish from Lake Michigan and Lake Superior wild lean strains from near Isle Royale differed. Elk Lake fish were more fusiform, elongate, and streamlined with a narrower caudal peduncle compared to hatchery lean strains and wild lean forms from the Isle Royale region of Lake Superior. The lake trout population in Elk Lake is a remnant of a now extirpated native Lake Michigan population that was established either by natural colonization or stocking from historical Lake Michigan populations. Elk Lake lake trout is as genetically diverse as other strains used in Great Lakes reintroduction efforts and likely represent a viable gamete source representing genetic diversity lost from Lake Michigan.     

European Valve Snail Valvata piscinalis (Müller) in the Laurentian Great Lakes Basin

Previously reported from the lower Great Lakes basin and St. Lawrence and Hudson rivers, the nonindigenous gastropod Valvata piscinalis was found for the first time in Superior Bay (Minnesota) of Lake Superior, Lake Michigan (Wisconsin), and Oneida Lake (New York) of the Lake Ontario basin. This snail was not abundant in Lakes Superior and Michigan, whereas in eutrophic Oneida Lake it reached a maximum density of 1,690 individuals/m² (mean density = 216 individuals/m²). Human-mediated disturbances could facilitate the range extension of this snail by providing dispersal opportunities (e.g., canals, shipping traffic) or increasing nutrients (e.g., eutrophication). A native of the Palaearctic region, V. piscinalis has colonized sites across the Great Lakes basin, suggesting that it will likely become common in disturbed Great Lakes areas.     

Monitoring Round Goby (Neogobius melanostomus) Population Expansion in Eastern and Northern Lake Michigan

In the Great Lakes basin, round gobies (Neogobius melanostomus) were first reported from the St. Clair River in 1990. Reported here are the details of range extension and establishment of round gobies in eastern Lake Michigan at Grand Haven, Michigan and in northern Green Bay at Escanaba, Michigan. Round gobies were first collected in survey samples at Grand Haven in 1997 (0.0 to 0.5 fish per trawl hour). Catch rates increased in 1998 (1.5 to 3.0 fish/h) and 1999 (38.0 to 69.0 fish/h). Individuals collected by trawling (N = 207) ranged in total length from 18 to 94 mm. Round gobies were first collected in survey (trawl) samples at Escanaba in 1998 (7.5 fish/h; total length range 43 to 58 mm). Round gobies were also collected during 1999 in trawls at Muskegon and in gill nets at Grand Haven and Saugatuck. No round gobies were collected at five other eastern Lake Michigan ports sampled during this same time period (1995 to 1999). Numerous adult round gobies were captured by anglers at Grand Haven and Escanaba, indicating that these populations had been established for some time prior to being detected in survey sampling. Additional populations were verified from angler reports at Charlevoix (1998) and Kipling (1999), Michigan. Round gobies collected by anglers were generally larger, and taken in areas that are difficult to sample using conventional inshore sampling gear. These results indicate that survey and angler samples are complementary, but that up-to-date angler reports of exotic species that bite readily (round gobies) or are otherwise collected by anglers (Bythotrephes cederstroemi, Cercopagis pengoi) are critical to tracking the spread of these organisms.     

Ultrasonic Telemetry Studies of Fish Activity Near the Nanticoke Thermal Generating Station

Nanticoke is a developing industrial centre on the north shore of Lake Erie on Long Point Bay. Ultrasonic telemetry studies were conducted in 1973–77 to determine the effects of Nanticoke Thermal Generating Station's warmwater discharge on movement patterns of smallmouth bass (Micropterus dolomieui), rock bass (Ambloplites rupestris), and yellow perch (Perca flavescens). A total of 74 fish were tracked in the station's effluent plume and at control locations. These fish were monitored continuously, recording position, distance between turns, swim speed and angle of course alteration, as well as various environmental parameters.An activity index was developed to measure the overall level of fish activity. The measured activity of all three species was significantly lower within the plume than outside of it. Water depth appeared to be the most important factor determining fish activity, followed by wave height, current speed, and temperature. Wave height, current speed, and temperature are directly affected by the thermal discharge. However, upon closer examination, the response to the plume appeared to have been principally rheotactic.No long-term residency in the plume was observed during this study or during concurrent mark-recapture studies.     

First Occurrence of Cercopagis pengoi in Lake Michigan

Adults and juveniles of the predaceous cladoceran Cercopagis pengoi, native to the Ponto- Caspian region, were found in nearshore waters of southern Lake Michigan during August and September 1999. This invasive cladoceran was previously reported from Lake Ontario, but this is the first report of C. pengoi from Lake Michigan. In Lake Michigan, densities of C. pengoi peaked at about 75/m3 on 22 September when water temperature was 16°C, and first and second instars comprised up to 90% of the samples. Of the third and fourth instar reproductive forms, parthenogenetic females were most abundant (up to 33% of all individuals sampled) and were present on all sampling dates. Males and females with resting eggs appeared in low abundance on the last two sampling dates perhaps in response to decreasing temperatures. The impact of this invader on the Lake Michigan food web is yet undetermined, but C. pengoi individuals were found in the stomachs of alewife on 22 September indicating that fishes will feed on C. pengoi.     

Biophysical Model of Larval Yellow Perch Advection and Settlement in Lake Michigan

Potential for large-scale physical transport processes to affect recruitment of Lake Michigan yellow perch (Perca flavescens) was studied by examining the variation in larval distribution, growth rate, and settlement during June–August 1998–2003 using a 3D particle transport model linked with an individual-based bioenergetics growth model. In all years, virtual larvae were released nearshore in southwestern Lake Michigan, a known and important spawning region for yellow perch. For any given year, the same circulation pattern and water temperature either promoted or reduced yellow perch settlement depending on the consumption rates and settlement size chosen in the growth model. Increased consumption increased the number of settled larvae and expanded the total area where larvae settled, whereas increased settlement size reduced the number of settled larvae and reduced the overall settlement area. Interannual variability in circulation patterns and water temperature also resulted in contrasting larval settlement rates, settlement locations, and size of settlement areas between years. Model predictions were most consistent with field observations of age-0 yellow perch from Illinois and Michigan waters when settlement was assumed to occur at 50 mm. Moreover, our model suggests that larvae originating from southwestern Lake Michigan can recruit anywhere within the southern basin and even in the northern basin. Future model improvement will require information on the relative contribution of various sectors to the larval pool, their distribution with reference to the hydrodynamic landscape, the feeding and growth of yellow perch during their pelagic phase, and the size at transition to demersal stage.